The invention relates to a process for producing a protected reduced supported metal catalyst powder, in particular catalysts used in a variety of chemical reactions, such as, the hydrogenation of hydrocarbon compounds in petrochemical and oleochemical processes; the hydrogenation of unsaturated fats and oils, and unsaturated hydrocarbon resins; and in the Fischer Tropsch process. This invention also relates to a composition comprising said catalyst and a liquid.
Hydrocarbon resins are produced by oligomerisation or polymerization of hydrocarbon fractions, typically originating from the (catalytic) cracking of crude oil, including petroleum distillates and fractions from naphtha crackers. In order to give the resin the required properties (chemical and physical), they are usually hydrogenated using hydrogenation catalysts. Most commonly nickel catalysts are applied in this process.
Hydrogenation can be used to modify various properties of the hydrocarbon resin. Examples of these modifications include the removal of part or all of the aromatic functionalities, removal of so-called colour bodies (decolorizing the resin from brown or yellow to white), modification of the molecular weight distribution, and removal of impurities, such as sulfur, nitrogen and/or halogen compounds.
Tailor made metal catalysts that fulfill these specific demands include nickel and palladium catalysts, which are generally delivered as reduced metal particles supported on an inorganic support. One such example is a nickel catalyst supported on silica/alumina.
Supported metal catalysts may typically be in the form of porous particles, a porous powder, or shaped as a monolith, a structured packing, tablets, extrudates, or spheres. Often catalysts in the form of a powder are used in the hydrogenation of resins.
However, such powdered catalysts can be pyrophoric or pyrogenic, with self-ignition temperatures typically much lower than room temperature. Such catalysts therefore need to be packed and shipped in a protected and/or stabilized way.
A common method used to stabilize such catalysts is to implement a controlled oxidation step after the reduction of the catalyst, such as described in DE-A-199 09 175. In this step the catalyst is exposed to oxygen in a controlled manner such that, for example, the outer layer of the reduced nickel particle is protected with a small layer of nickel oxide. This stabilization step, however, is time consuming and the resulting product is undesirable as it generally consists of small, dusty and toxic particles. Furthermore, this method only results in a moderate increase of the self ignition temperature.
Shaped catalysts are typically stabilized by immersion in a protective liquid. Upon handling of the protected shaped catalyst, the excess liquid is removed and the shaped catalyst is then loaded into the reactor. Powder catalyst may also be stabilized by this method which would result in a slurry. However, the disadvantage of this method being applied to a powder catalyst is that the powder catalyst tends to settle, which leads to difficulties in handling of the stabilized powder catalyst, in particular when loading into a reactor.
EP-A-0 572 081 describes coating a catalyst powder with a protective grease. The disadvantage of this method is that the grease coating would have to be removed to prevent contamination when used in applications not involving grease. In many applications such contaminations are unacceptable.
WO-A-2004/035204 describes a process for protecting a reduced catalyst powder by dispersion in hardened vegetable oil or fat to produce catalyst flakes or droplets. Again, that method can only be applied if the oil or fat does not contaminate the product.
U.S. Pat. No. 6,294,498 describes a process for protecting a solid catalyst by coating the external surface with a polymer. U.S. Pat. No. 6,294,498 describes that the amount polymer coating should be less than 25% of the weight of the catalyst. Further, that the polymer is applied at a temperature below the crystallization point of the polymer.
JP-A-8 024 665 describes using a non-volatile oil to protect a metal catalyst from deactivation and ignition. Again, the disadvantage of this method is that the protective coating must be removed using additional chemicals This document also describes that this method may be used to produce a paste, which has the disadvantage that it is a less convenient form for shipping and handling.
U.S. Pat. No. 3,453,217 describes protected catalyst particles which have a cylindrical shape. Catalyst powders are not disclosed or suggested.
EP-A-0 249 849 describes protecting a shaped catalyst by impregnation of said catalyst with one or more liquid alcohols under an inert atmosphere.